1. Field of the Invention
The present invention relates to medical, industrial and material processing applications requiring the delivery of optical radiation by fiber optics, and more specifically, it relates to a means for coupling the output of a semiconductor laser diode array into a fiber optic.
2. Description of Related Art
Laser diodes provide an efficient and compact technology for converting electrical power directly into coherent light. However, because the radiation produced by these devices is highly divergent in at least one spatial direction, it has been problematic to efficiently couple their radiation into optical fibers. Diode bars are the highest average power and the most mature form of semiconductor laser diode arrays.
U.S. Pat. No. 5,436,990, directed to an apparatus for coupling a multiple emitter laser diode to a multimode optical fiber, discloses a small diameter multimode optical fiber with a low numerical aperture (i.e., 0.1) that is used as a microlens to collimate the output emissions of a laser diode before butt coupling the output of the laser diode to an optical fiber. The optical fiber used as the microlens is chosen such that its diameter roughly equals the diameter of the fiber to be coupled to the laser diode. One end of the fiber is mounted in a fixed position and the other en the fiber is slip fit into the end of a hollow receiving member mounted in a fixed position and running parallel to the axis of the fiber. The collimation is performed in the high NA direction of the output of the laser diode. The output of a bundle of butt coupled optical fibers may be used to pump a laser system.
U.S. Patent No. 5,333,077, directed to a method and apparatus for efficient concentration of light from laser diode arrays, discloses a lens system for use with a light beam having a spatial cross-sectional distribution which is extended predominantly in one direction, including a first optical element for receiving and redirecting different portions of the light beam to different locations on an imaginary plane wherein at least two portions of said light beam are directed along two non-parallel paths so as to generate a two-dimensional pattern of light on the imaginary plane; and a second optical element located at the imaginary plane and aligned with the two-dimensional pattern of light for redirecting each portion of the two-dimensional pattern of light to a focal point. Alternatively, the lens system of the invention may be used to receive and redirect to a focal point each individual light beam of a linear array of light beams, or each portion of a two-dimensional light beam, or each individual light beam of a two-dimensional array of light beams.